The use of unmanned aerial vehicles (“UAVs”) for delivering munitions to a target is known. In some cases, these UAVs are configured as remotely controlled missiles, in that they are configured to detonate upon reaching the target. Because these are typically limited-use or single-use or devices, the cost of each UAV is a critical design parameter.
For large single-use UAVs, the cost, size and weight of a guidance system component such as a camera on a two-dimensional gimbal may not be very significant. However, for very small UAVs, the cost, size and weight of such a system component can be very significant. Thus, very small UAVs must be designed with minimal complexity in their systems.
Modern rules of engagement may require that a positive identification (“PID”) of a target be established prior to initiating an attack while used within theatres of operation that may contain civilians. Typically, the PID must be maintained from a time prior to an activity that commits to the initiation of the attack, throughout a terminal phase of the attack. Additionally, in such theaters modern rules of engagement may require that a potential target be established as a legitimate target prior to reaching a wave-off requirement, i.e., a period of time (e.g., 5 seconds) prior to completing the attack.
With reference to FIGS. 1A and 1B, a remotely controlled aircraft 10 that is equipped with a forward-looking camera 20, a side-looking camera 30 and an integrated explosive. The forward-looking camera 20 has a limited forward field of view 22 and a separate side field of view 32 is provided by the side-looking camera 30. This configuration provides for the aircraft to first locate a potential target 51, and then loiter in a pattern 53 around the target until an operator/pilot of the aircraft establishes that the aircraft has a PID on a target that is a legitimate target. As shown in FIG. 1B, one loitering technique is to fly the aircraft 10 in a geometric pattern (e.g., a circle) around the potential target until the legitimacy of the target 51 is established. In doing so, the side-view camera 30 maintains a continuous view of the potential target within its field of view 32, and therefore it maintains a PID on the potential target so long as there are no obstructions. The velocity vector is roughly 90° off of the direction towards the target. The pattern 53 may be flown at a higher altitude than that of the glide path of an attack on the target.
In a target-approach maneuver, when the legitimacy of the target is established, the aircraft operator commits to the action at a ground commit-location 55 (a spot on the ground under the location where commit action was done), and flies an approximately 90° turn 57 to fly outbound, away from the target (on an outbound leg 59), for an appropriate distance. During this portion of the flight, the altitude may be reduced. The aircraft then flies a 180° turn 61 to fly inbound toward the target on an inbound leg 63.
The 90° turn 57 is not as tight as the 180° turn 61 (i.e., the radius of the 180° turn has a smaller radius). This places the ground commit-location 55 in which the 90° turn was initiated between the ground locations of the aircraft and the target 51. Thus, on the inbound leg, the aircraft returns to the ground commit-location 55 over which it initiated the 90° turn, having a velocity vector that is toward the target rather than roughly 90° off of that direction. This can be accomplished using inertial navigation and/or GPS. The inbound leg 63 includes an initial approach 67 leading from the 180° turn 61 to the ground commit-location 55, and a final approach 69 leading from the ground commit-location 55 to the target 51.
Because the aircraft loses sight of the target 51 throughout a portion of this outbound-and-inbound maneuver, the aircraft must reestablish PID on the target once it is visible in the forward-facing camera 20. Because PID is lost during these maneuvers, the aircraft operator must then reestablish that the target is the previously identified legitimate target.
This outbound-and-inbound maneuver provides a number of advantages. First, it allows for the aircraft altitude to be reduced to a preferable glide path on both the outbound leg and the inbound leg. Second, it provides for the aircraft's velocity vector to be turned toward the target. Third, it provides for a longer approach to the target, and therefore more time for the operator to reestablish that the target is a legitimate target. Fourth, it allows for an attack through a narrow window of attack vectors, such as could occur when the target is located around or between tall buildings 65.
Nevertheless, it also has drawbacks, in that requires a substantial amount of time to complete, and that it places the aircraft over more terrain at reduced altitudes. This potentially allows observers in the area, to detect the aircraft and raise the alarm. Moreover, the time for this extended maneuver allows time for a mobile target to depart, even if the aircraft is not detected. Also, after the PID is lost on the outbound leg, the legitimacy of the target must be reestablished on the inbound leg, raising the possibility that the legitimacy might not be reestablished prior to having to abort the attack.
It should be noted that in FIG. 1B, the sizes of the various portions of the flight paths, and the sizes of the aircraft 10, target 51 and obstructions 65, are not necessarily representative of actual conditions. Rather, they are sized to clearly illustrate the concepts of the maneuver.
Accordingly, there has existed a need for an armed aircraft that is loitering around a target to be able to reduce its altitude to the level of a preferable glidepath, turn its velocity vector toward the target, and not lose time reestablishing that the target is legitimate, all while not incurring significant risk of exposure. Preferred embodiments of the present invention satisfy these and other needs, and provide further related advantages.